This invention relates to improvements in the photo-transmission portion of a spark detector system and, more particularly, is directed to a readily replaceable light rod assembly for coupling infrared energy to a photoelectric sensor element in such a system.
Conventional spark detection and extinguishing systems, such as those sold in this country by Clarke's Sheet Metal, Inc. (the assignee of applicants) and FagusGrecon, Greten GmbH and Co. KG, utilize a fiber optic "polyp," consisting of fiber optic bundles joined together as a trunk at one end to form a single output and divided at the other end into a plurality (typically, three) of limbs which serve as inputs, or photo energy gatherers, for coupling photoelectric energy, such as the thermal energy generated by a spark in a zone or region being monitored, to a sensor element for converting that energy into an electrical signal for processing by the spark detection and extinguishing system.
Conventionally, three input fiber optic bundles, coupling to a single output and spacedly arranged in a circular configuration around the periphery of a zone, are required to effectively monitor a region. A typical application for such systems is in flow pipes and conduits, referred to hereinafter as ducts, through which fine particulate matter such as wood particles or grain are conveyed at high speed by pneumatic action. In such applications the appearance of a spark, caused for example by a foreign body frictionally rubbing against the interior surfaces of the conduit, if not rapidly detected and quickly extinguished, can lead to an explosion and/or fire, with destructive consequences. Thus, systems of the type referred to above have been developed to monitor for the presence of sparks in one or more zones through which the particulate matter flows and then, when a spark is sensed, to actuate appropriate mechanisms, such as water spray valves, to extinguish the spark and also to sound alarms.
As noted, the aforementioned polyps are used as a pick-up or input device for coupling the thermal energy in the infrared and near infrared light spectrum developed by a spark to a photoelectric sensor element that converts the detected energy into an electrical signal. However, these polyp devices have certain disadvantages that limit their effectiveness, as well as the ease and cost of their maintenance and repair. For example, one of the principal disadvantages of the conventional polyp configuration of fiber optic bundles is that, if any one leg of the polyp is damaged, the unit must be replaced in its entirety. In addition to the cost involved, the replacement of a polyp unit is relatively time consuming and labor intensive, since the input or limb ends, with typically three being required to effectively cover a monitoring zone, must each be individually removed, and then the limbs of a replacement polyp installed at each location in place of the removed limb.
Another disadvantage of the conventional polyp assembly is that, as previously mentioned, three are required to effectively cover a single zone, since the viewing angle of an individual fiber optic limb is only about 65.degree..